Don’t be fooled by the name—Iceland is one of the hottest hotspots in the world, geologically speaking. The island’s volcanic legacy reared its head again yesterday as a massive eruption by a volcano beneath a glacier caused the evacuation of hundreds of residents and created ash clouds that delayed flights all around Northern Europe.

The volcano, called Eyjafjallajokull, rumbled last month, but that was nothing like this. “This is a very much more violent eruption, because it’s interacting with ice and water,” said Andy Russell, an expert in glacial flooding at the University of Newcastle in northern England. “It becomes much more explosive, instead of a nice lava flow oozing out of the ground” [AP]. The flood caused by melted glacial ice caused the evacuation about 800 people. Waters threatened to spill over onto Highway 1, Iceland’s main highway that makes a circuit around the island. But some quick digging by construction crews altered the course of the water.

The huge cloud of ash meandered to the south and east toward the United Kingdom, and probably will move over mainland Europe before it finally dissipates. As a precaution, yesterday British aviation authorities totally closed the nation’s airspace. The move effectively grounded all flights in Britain from 11 a.m. local time and affected an estimated 6,000 flights that use British airspace every day, aviation experts said. Oddly, for travelers, the closing was announced under clear blue skies [The New York Times]. The altitude of the ash cloud made it difficult to see from the ground.

The main aviation risk posed by the ash cloud wasn’t that it would interfere with visibility, experts say, but rather that the fine silicate particles can seriously damage airplane engines. The particles can clog ventilation holes, causing the jet engines to overheat. Says vulcanologist David Rothery: “Air traffic restrictions have very properly been applied…. If volcanic ash particles are ingested into a jet engine, they accumulate and clog the engines with molten glass” [BBC News].

Despite the flight cancellations, scientists tried to assure people in Britain that the ash wasn’t heavy enough to be a public health concern. In fact, it’s nothing compared to the worst eruptions to happen in Iceland, according to vulcanologist Dougal Jerram. “One of the most influential ever eruptions was the 1783-1784 event at Laki in Iceland when an estimated 120 million tonnes of sulphur dioxide were emitted, approximately equivalent to three times the total annual European industrial output in 2006. This outpouring of sulphur dioxide during unusual weather conditions caused a thick haze to spread across Western Europe, resulting in many thousands of deaths throughout 1783 and the winter of 1784″ [BBC News].

The danger this time around is that Eyjafjallajokull will trigger an eruption of its more powerful neighbor, Katla. That happened back in 1821.

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Image: Wikimedia Commons / Chris 73; USGS